The telephone, power, cable television, and other industries have long made use of enclosures or housings for protecting above ground connections between underground wires and cables and components attached to these cables and wires. These connections between cables and wires and the components often involve a valuable investment and must be protected from the outside environment by the protective enclosure or housing.
A cable is defined broadly and includes conventional metal cables used in telecommunications and power applications as well as fiber optics cables, cable television cables and the like. Cable components may encompass conventional telephone cable connectors or other items such as terminal blocks for power and telephone lines, fiber optics connectors, amplifiers, power supplies, distribution devices and many other cable related devices.
The outside environment contains both natural and human threats to the above ground connections to cables. Examples of human threats include malicious vandalism or premeditated entry. Natural threats are further broken down between above ground and below ground environmental threats. Above ground threats may include acid rain, wind driven rain, snow, dirt, insects and ultraviolet rays for example. Below ground threats may include rodents, insects, and ground moisture. All three of these outside environmental threats, human, above ground, and below ground, pose specific problems for the protection of the cables and cable components contained within the protective enclosures.
The protective enclosures are designed to minimize or eliminate the exposure of the cables and or cable components to these outside threats. The protective enclosures are thus fabricated from materials that are durable and long lasting. Such materials may be metallic such as steel or non-metallic such as fiberglass or plastic. Enclosures have a wide variety of configurations and sizes which reflect among other factors the many different cable diameters and the number of cables or wires to be brought into the enclosure. An enclosure may be made of one part or require the assembly of many parts. When assembled, all enclosures have one end that is located in contact with the ground at or near ground level or below ground level. Underground cables are brought up through this end to the interior of the enclosure.
All protective enclosures are designed to deal with the environmental threats through features in their engineering. The enclosures also must be designed so as to be easily and quickly disassembled and reassembled for access should additional work have to be performed on the cables and or cable components contained therein. Presently, current enclosures have successfully excluded most threats from harming the cables and cable components contained within the enclosure while allowing easy access to the interior of the enclosure if desired. For example, an enclosure built of heavy duty material is usually sufficient to prevent vandalism. It is also sufficient to prevent snow, dirt, rain, insects and rodents from accessing its interior to harm the cables and or cable components inside. One notable threat which is not presently protected for while allowing easy access to the cables and cable components within the enclosure is that of ground moisture.
Ground moisture is prevalent in all climates and areas including the driest regions. After a protective enclosure is assembled and put in contact with the ground, ground moisture will migrate through the openings used to transmit the cables to the interior of the enclosure. This ground moisture will periodically condense inside the top end of the enclosures. The amount of time for condensation and the amount of condensation will vary based on several factors. These factors include the type of material used to construct the enclosure, the outside temperature, and the time of day.
When enough moisture has condensed on the inside of the top end of the enclosure, it will drip onto the cables and or cable components, causing corrosion, degradation and or failure of performance. This phenomenon poses a major threat to the cables and or cable components i.e. the investment.
Thus, a moisture barrier is required to prevent ground moisture from migrating through the cable accesses of the protective enclosures. A non-porous, non-hydroscopic barrier is preferred to block moisture from moving up into the interior of the enclosure. The barrier must be inexpensive, and be easily and quickly installed in the wide variety of enclosure configurations. The barrier must also be easily and quickly removed and reinstalled when additional cables and or cable components are added.
Previous attempts to reduce or eliminate the ground moisture problem have included placing water proof sealing chambers made of materials such as foam around the cables and or cable components. The sealing chamber is usually cemented or glued onto the components or molded to snugly fit the cables. Another solution has been to pour expanding foam within the confines of the base, allowing the foam to form a barrier. Unfortunately, such sealing materials are difficult or impossible to remove once they have been installed. Such materials are also very costly. In addition, such materials are installed permanently and may not be readily replaced when repairs need to be made or when additional cables or components need to be connected in the enclosure.